The invention relates to a device for sealing a rotating shaft penetrating a stationary housing wall relative to the two housing sides. The device comprises a sealing ring arranged between the housing wall and the shaft and fixedly connected to the housing wall. The device also comprises means for supplying sealing oil into the sealing gap between the inner wall surface of the sealing ring and the outer wall surface of the shaft, wherein the sealing ring in its sealing surface in the area of the means for supplying sealing oil has pocket-shaped recesses extending in the circumferential direction. The pocket-shaped recesses of the sealing ring are closed off at least on one side of the sealing ring and sealed relative to the adjoining space of the correlated housing side by a circumferential boundary stay.
A special field of application of the invention are so-called turbo generators for generating electric energy. In turbo generators having great output, cooling is realized by means of hydrogen (or another type of gas) that is located within the generator housing. For this purpose, a gas-tight passage of the two shaft ends of the rotor through the generator housing is required in order to prevent escape of hydrogen relative to the two housing sides in the area of the rotating shaft.
The sealing of the shaft in the housing is realized by a shaft seal that is arranged fixedly in the housing and surrounds the rotating shaft. In this connection, by means of an appropriate sealing oil supply an oil film is maintained between the rotating shaft and the floating sealing ring that is stationary. For all operating states it is therefore required that the sealing oil as a barrier medium completely fills the sealing gap between the shaft and the sealing ring. Moreover, the axial gaps between the lateral surfaces of the sealing ring and the sealing ring housing in general are filled with sealing oil. This arrangement of the sealing ring and the shaft form a system that can oscillate because the oil film provides a spring-damper system.
However, for a completely centered ring with constant gap size, a self-centering action cannot be realized. This results in increased eccentricities of the sealing ring. This causes irregular heating, thermal buckling, increased hydrogen consumption, lower hydrogen purity as well as generally increased wear.
For this reason, there are self-centering sealing rings that essentially center themselves automatically in all operating states on the sealing oil film. This is achieved in that the sealing ring has about its inner wall surface several pocket-shaped recesses for the sealing oil. These pocket-shaped recesses have in the rotational direction of the shaft a wedge-shaped contour. The advantage of these pocket-shaped recesses in the sealing ring resides in that, at a reduced spacing between the shaft and the sealing ring, pressure builds in the pockets and, in turn, centers the sealing ring. This pressure generation is present also in the case of a centric ring.
The disadvantage of the sealing ring used in this sealing device resides in that the pocket-shaped recesses in the axial direction of the shaft are configured to be continuous, i.e., they extend from one side of the sealing ring to the other side of the sealing ring. In this way, viewed in the axial direction of the shaft, a continuous opening is formed. The result is that the effect of stabilization and self-centering cannot be completely realized.
U.S. Pat. No. 3,756,673 shows therefore a further developed device of the aforementioned kind for sealing and supporting a shaft penetrating a machine housing. In the embodiment according to FIG. 1 between the machine housing and the shaft a sealing bushing is arranged that is secured fixedly by means of a pin in the machine housing. The sealing bushing has at its inner circumference three sections. The two outer sections are provided for sealing relative to the high-pressure side and the low-pressure side, respectively, and the central section serves for radially guiding the sealing bushing relative to the shaft and for supporting the weight of shaft and rotor. The two outer sections rest seal-tightly against the shaft. The central section arranged therebetween, however, has wedge-shaped recesses for providing wedge-shaped hydrodynamic sliding films. They secure the sealing bushing strictly centrally relative to the shaft and prevent thus a metal contact in the two outer sealing sections. In the configuration of FIG. 2, the sealing bushing is laterally open in its central section. Therefore, a separate bushing is provided in this area.
U.S. Pat. No. 3,915,459 shows a sealing arrangement for a shaft that is rotatably supported in a housing. The seal has at its inner side an arc-shaped recess that is in communication with the oil supply by means of bores.
WO 89/09357 shows a so-called dry seal without oil lubrication for a rotating shaft. The seal is provided at its inner side with circumferential sealing chambers.